Orthogonal Frequency Division Multiplexing (OFDM) is a known technology for wireless communication that has the benefit of low equalization complexity. Currently, Wi-Fi utilizes OFDM for both its uplink and downlink transmissions, and LTE utilizes OFDM for its downlink transmissions.
One way to increase the transmission rate of an OFDM signal without increasing its equalization complexity is to relax the orthogonal nature of the signal; however, this increased rate may come at the expense of a more complex detection algorithm at the receiver. One way to achieve this increased transmission rate is by increasing the number of subcarriers in one OFDM symbol, while preserving its duration and bandwidth. Such a modulation technique is referred to herein as Non-Orthogonal Frequency Division Multiplexing (NOFDM). In an example of a NOFDM system, a plurality of non-orthogonal carriers is utilized for transmission. As used herein, a plurality of non-orthogonal carriers is a set of carriers in which at least some of the carriers are non-orthogonal to each other. In such a system, the plurality of non-orthogonal carriers may also include carriers which are orthogonal to each other.
Aspects of NOFDM are known to those skilled in the art; however, NOFDM has not been adopted in any standards due to its inability to deliver significant improvement in capacity over the capacity delivered by OFDM. There is a need for a NOFDM technique that provides an improvement in capacity over the capacity delivered by OFDM, while maintaining a low equalization complexity.